The known belt-stripper systems are used for a wide variety of conveyable materials and under extremely different conveying conditions. They always have to operate reliably even in the event of bulk-material properties that change quickly, for example outdoors when rain sets in, and at considerable distances from repair workshops, for example in the extraction of raw materials, wherein long service lives are required. Since it is usually the case that production stoppages result in high follow-up costs, the stoppage times should be kept as brief as possible.
These requirements are met by a modular construction. Conventional modules, as are described by way of example in EP 254 977 B1 and DE OS 36 20 960, have:                a base, which is attached to one of the carriers,        and a stripping body comprising                    a cutter carrier, to which a stripping blade is attached,            a bushing, in which the cutter carrier is rotatably mounted, and            a stripping edge unit, which is attached to the stripping blade,                        a joint having a torsion spring, the joint connecting the base and stripping body via a rubber torsion spring.        
It is usually the case that a plurality of belt-stripper modules are arranged one beside the other on a system carrier. Long service lives are also achieved by the stripping blades having wear-resistant carbide stripping edge units.
Such a belt-stripper module which is intended for a stripping apparatus for the return region of conveyor belts and is installed as one of a plurality of belt-stripper modules on a height-adjustable system carrier is also described in DE 10 2013 006 821 A1, and has the following features:                a base, which is fastened to the system carrier,        a cutter carrier, to which a stripping blade having a stripping edge unit is attached, the stripping blade forming an obtuse angle β in relation to the belt in the running direction,        a stripping body having a joint housing which has two joints and in which        a first joint, of which the axis of rotation extends transversely to the running direction of the belt and which has a torsion spring, connects the base and stripping body, the torsion spring pressing the stripping blade onto the belt in the process, and the first joint is provided with a spring-angle-measuring means and with a fixed stop for the deflection,        a second joint, of which the axis of rotation extends longitudinally in relation to the running direction of the belt and which has a bushing, in which the cutter carrier is rotatably mounted, orients the cutter carrier on the running belt such that the stripping edge unit always rests against the belt in a planar manner, and        a means for adjusting the height of the belt-stripper module on the base.        
In this case, the belt-stripper modules are arranged one beside the other on a system carrier such that the stripping blades, as seen in a plan view, are oriented precisely at right angles to the running direction of the belt. As seen from the side, the stripping blade, in contrast, forms an obtuse angle in relation to the belt, wherein said angle changes slightly in accordance with wear over the course of the service life.
A long-known problem with belt conveyors is that a large number of bulk materials, e.g. oil sands, tend to stick together and thus clog up the belt-stripper modules. The belt-stripper modules therefore have to be configured such that the largest possible through-passage surface area remains between the individual modules and the belt-stripper modules provide few opportunities for the bulk material to build up.
A further difficulty arises in the case of belt strippers where there are offset belt strippers pressing against an elastic belt in two or more rows arranged one behind the other. This gives the belt undulating characteristics, which adversely affect the stripping action. Added to this is the fact that, in the case of a plurality of belt-stripper modules above a system carrier, the stripping action of the individual belt-stripper modules overlaps. This gives rise to further problems relating to wear being non-uniform.
The largest possible through-passage surface areas are achieved for pulling-action belt-stripper modules when these are positioned slightly obliquely. Such belt-stripper modules are already known. Thus, U.S. Pat. No. 3,504,786 describes such an arrangement, FIG. 2 of this document showing an apparatus in which merely the stripping blades are positioned obliquely, and FIG. 3 showing an apparatus in which both the stripping blades and the cutter carriers are oriented obliquely in relation to the running direction of the belt. It is also shown here (reference sign 40) that the material is removed obliquely at the side, which gives rise to a reduction in the tendency of the material to build up. The obliquely positioned cutter carriers, however, are not mounted in a rotatable manner and cannot automatically orient themselves on the belt.
Scientific experiments have also proven the advantages of obliquely positioned strippers. These are described by “Zhang, Dynamisches Verhalten von Stahllamellen-Abstreifern an Gurtforderern, Universitat Hannover, [Zhang, Dynamic Behaviour of Steel-Blade Strippers on Belt Conveyors, University of Hannover], Dissertation 1982”. This dissertation determined, inter alia, that the cleaning capacity markedly increases if the blades are positioned obliquely.
Although the advantages of obliquely positioned belt strippers—as outlined above—are perfectly well known, it has not been possible for obliquely positioned strippers to become widespread in practice.